The steel process step by step

After the melting phase, dry additives are added. Due to the high temperature, the addition of liquids is not possible, as this poses a risk of vapour explosion. In this process step, ceramic valves, hoses and pipes are used, dimensioned to withstand heavy abrasive wear and high thermal stresses.

The steel refining process

Transport and storage of acids

For the internal transport of acids from the raw acid station, centrifugal pumps are mainly used. Magnetic drive pumps are particularly recommended for safety reasons, as they are leak-free. From the raw acid station, the acids are usually pumped to a mixing tank. For this purpose, we can offer different types of tanks, such as dual laminate tanks, i.e. fibreglass tanks with an internal polymer liner that provides high corrosion resistance. These are also referred to as lined tanks. When handling hydrofluoric acid (HF), for example, fibreglass is generally avoided. In such cases, tanks made of homogeneous polymer materials, such as HDPE (high molecular weight polyethylene), are recommended instead. For these mixing tanks, static mixers can be used to advantage.

We sell plastic valves made of PP and PVDF for these applications. In cold outdoor environments, we recommend fluoroplastic lined steel valves as these valves can withstand temperatures between -60 and 200 degrees C. In environments with acids, the air is corrosive and needs to be ventilated. This is done with the help of GRP pipes, GRP fans and larger dampers made of various polymeric materials.

prayer bath

Different acids are used depending on the type of steel to be pickled. When pickling carbon steel, sulphuric acid or hydrochloric acid is used. When it comes to stainless steel AISI 304 or acid-resistant steel AISI 316L, a mixed acid of, for example, 5% hydrofluoric acid, HF, and 20-25% nitric acid, HN03, is used. We can manufacture pickling tanks in lined glass fibre, GRP. The pickling tanks are heated with the help of heat exchangers, and we have both plastic and graphite heat exchangers to offer.

The pumps we recommend are shaft-sealed linear centrifugal pumps. Due to the metal particles, we cannot use magnetic drive pumps. In the environment around the pickling bath, we can offer gratings and supporting structures that can withstand the corrosion environment - these are made of glass fibre, GRP. In combination with the pickling bath, the choice of valves depends on the temperature. For the regeneration stage that comes when the pickling sludge is emptied, we mainly use linear centrifugal pumps.

Acid neutralisation department

The acid neutralisation section that comes after the regeneration, lime is used to neutralise the acid back to pH 7. If lime milk is used, we pump it with a centrifugal pump. On the other hand, if we use dry lime, we can use a hose for handling these in combination with a sending vessel. When we neutralise the milk of lime, we use a dynamic mixer in the lime mixing vessel. When we pump milk of lime, we need to use continuous flushing and then we use a so-called quench tank, otherwise the lime clogs the pump. The valves used in this step are usually hose valves, which at neutral pH can be made of natural rubber.

Filter press

The sludge produced after neutralisation is sent to a chamber filter press. To transport this sludge, we cannot use a normal centrifugal pump but use a filter press pump with 14-15 bar outlet pressure.

The internal treatment plant

This stage, which includes flocculation and sludge handling, requires both dosing pumps and, for example, hose pumps.